A battery operated microprocessor system, using low power CMOS technology, provides control of a portable infusion pump. This programmable system is compact enabling a patient to wear it, and it provides sufficient power for drug infusion periods up to one week. A major feature of the controller is the ability to program a fairly complex infusion sequence in contrast to the standard repetitive sequence delivery systems which are available. Programming variables are the time of day for infusion, the infusion duration, the rate of infusion during the infusion period. These variabled are entered via a keypad in response to prompts given on a display which in normal operation shows, the time of day. The ability to be able to establish a defined infusion pattern allows the drug delivery to be correlated with the biological clock. The system is not restricted to any particular drug infusion schedule and can be applied to many drug delivery applications.